Cannot add or remove object to an Array in Firebase Firestore using Flutter

Question

I'm trying to add an object to an array in Firestore. My code is

Future signUpForClass(String docId, Member member) async {
    await _fireStoreInstance.collection("collection_name").doc(docId).update({
      "signedUpMembers": FieldValue.arrayUnion([member])
    });
  }

but I get an error saying: Invalid argument: Instance of 'Member'

When I check on the empty array in Firestore it seems like the type of the array is a String and I am able to use a string argument, i.e. member.name, and then I can add/remove from the array. However, when I create the document with the "signedUpMembers" array, I pass the array an empty list of Members, i.e. "signedUpMembers": <Member>[]

What am I doing wrong? I've tried a bunch of different syntax for this but I haven't been able to add the whole object to the array, only strings.

Pretty sure Firestore doesn't support storing your object. See: firebase.google.com/docs/firestore/manage-data/data-types — GrahamD
– GrahamD, Commented Feb 1, 2021 at 16:34
I think you need something like this flutter.dev/docs/development/data-and-backend/json — Gerpea
– Gerpea, Commented Feb 1, 2021 at 16:36

Rehmat Singh Gill · Accepted Answer · 2021-02-01 16:39:01Z

1

Firebase Firestore only allows certain data-types (String, List, Map, GeoPoint, etc). To store your data, you should convert it to json/map.

class Member {

  String name;

  ...

  Map toJSON() {
    return {
      'name': name,
      ...
    }
  }
}

answered Feb 1, 2021 at 16:39

Rehmat Singh Gill

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